Epigenetic clocks, however, are most commonly created using blood, not saliva, which is why the researchers in this study said they wanted to compare the performance of different tissue-sample types.

The immune system is the body’s tool for preventing or limiting infection. Its complex network of cells, organs, proteins, and tissues enables the immune system to defend the body from pathogens.

Are Blood Type and COVID-19 Linked? Several studies have examined whether certain blood types are more susceptible to coronavirus infections and severe disease, and while researchers have found ...

Anemia is when you have low levels of red blood cells. When this happens, your organs and tissues have a harder time getting oxygen. You may feel fatigue, weakness, and shortness of breath.